1. Field of the Invention
The present invention relates to a method of manufacturing a high-accuracy ink jet recording head.
2. Description of the Related Art
An ink jet recording head is a recording head of discharging ink on a recording medium such as a sheet of paper, a resin sheet or the like by utilizing the function of an energy generating element such as a piezoelectric element, a heat element or the like to display a character, a sign, a figure and the like. The ink jet recording head is produced by using a semiconductor film formation technique using photolithography on a substrate, and there is known one building therein an electric control circuit for driving the energy generating element in response to a request of miniaturization and densification.
As these methods of manufacturing an ink jet recording head, ones disclosed in U.S. Pat. No. 5,478,606 and U.S. Pat. No. 6,390,606 are known. In the following, a description is given by using FIGS. 4A to 4F. As shown in FIG. 4A, a substrate 21, on which a plurality of energy generating elements 22 such as heating resistors are arranged, is used, and a sacrifice layer 25 is provided at a position of forming a through-hole for forming an ink supply port, which will be described later. A protective layer 24 is laminated on the sacrifice layer 25 and the energy generating elements 22 to cover them. A substrate which is made of a silicon single crystal having a crystal orientation 100 and the whole back surface of which is covered by a SiO2 film 23 is used as the substrate 21.
As shown in FIG. 4B, a polyether amide resin is coated on the protective layer 24 on the front surface of the substrate 21 and on the SiO2 film 23 on the back surface of the substrate 21, and the polyether amide resin film is heated to be cured. Then, the cured polyether amide resin on the front and the back surfaces of the substrate 21 is patterned by the photolithography to form polyether amide resin layers 26 and 27. The polyether amide resin layers 26 and 27 are formed by coating a positive type resist on the cured polyether amide resin by a spin coat method or the like to expose and develop the coated resist. Then, after the polyether amide resin has been patterned by dry etching or the like, the positive type resist remaining at non-exposed portions caused by a mask (the portions on the polyether amide resin layers 26 and 27 which have not been etched) is exfoliated.
As shown in FIG. 4C, a positive type resist that can be dissolved by a solution is coated at a portion to be a flow path of ink to form mold materials 28 patterned by the photolithography.
Next, as shown in FIG. 4D, a covering photosensitive resin is coated on the mold materials 28 by the spin coat method or the like to form a flow path forming member 29. A water repellent material 30 is formed on the flow path forming member 29 by laminating a dry film made of a water repellent resin or the like. Ink discharge ports 31 are formed in the flow path forming member 29, on which the water repellent material 30 is laminated. The ink discharge ports 31 are formed by patterning the flow path forming member 29, on which the water repellent material 30 is laminated, by the photolithography using an ultraviolet (UV) ray, a deep UV ray or the like.
As shown in FIG. 4E, the front surface and the side surface of the substrate 21, on which the mold materials 28, the flow path forming member 29 and the like are formed, are covered by a protective material 32 by the spin coat method or the like.
As shown in FIG. 4F, an etching starting surface for forming the through-hole of the substrate 21 on the SiO2 film 23 on the back surface of the substrate 21 by the dry etching using the polyether amide resin layers 27 as masks.
Next, anisotropic etching by wet etching is performed from the etching starting surface of the back surface of the substrate 21. After the end of the anisotropic etching of the substrate 21, isotropic etching of the sacrifice layer 25 is continuously performed by the strong alkali solution used for the wet etching to form the through-hole in the substrate 21, and then an ink supply port 33 is formed. After that, the polyether amide resin layers 27 and the protective material 32 are removed by the dry etching, and the mold materials 28 are eluted from the ink discharge ports 31 and the ink supply port 33 by a solution to form an ink chamber space.
The substrate 21, in which a plurality of ink chambers are formed by the processes described above, is cut to be separated and to be made to be chips with a dicing saw or the like, and electric joining for supplying electric power to the energy generating elements 22 is performed. Then, the substrate 21 is connected to an ink supply path connected to an ink storage portion, and consequently an ink jet recording head is obtained.
In the manufacturing method described above, the polyether amide resin layers 26 are used for enhancing the adhesion property between the substrate 21 and the flow path forming member 29.
The manufacturing method described above is one excellent in utility, but an ink discharge rate is very small, and has a limitation in dimension designing because the finished dimension tolerances of the adhesive layers and the wall members of the flow paths are different from each other in the case where a head in which the arrangement density of its discharge ports is high (for example, a head having a discharge rate of 1 pl and the arrangement density of its discharge ports is 1200 dpi) is manufactured. Moreover, there is a case where the adhesion forces between the adhesive layers and the wall members of the flow paths lower owing to the finished dimensional tolerances of the adhesive layers and the mold materials or a case where an ink discharge performance is affected by the tolerances.